Point-of-care diagnostic devices require numerous on-chip structures to manipulate fluid and sample flow. At times, such structures require complex lithography to provide miniaturized components. Rapid prototyping (e.g., laser cutting) can greatly simplify manufacturing, but many component designs cannot be rapidly prototyped without losing function. Accordingly, there is a need for more robust designs that can provide desired hydrodynamic functionalities while being manufactured in a rapid manner.